If you look at the right square (L3 switch) there is a line pointing to a static route. The 100mb MetroE is terminated directly into the SFP slot on that switch. I'm trying to figure out the best way to redistribute the static route on that switch to the other devices. I'm also trying to understand what will happen when we lose that MetroE link if it's a static route.

robert.juric wrote:
If you look at the right square (L3 switch) there is a line pointing to a static route. The 100mb MetroE is terminated directly into the SFP slot on that switch. I'm trying to figure out the best way to redistribute the static route on that switch to the other devices. I'm also trying to understand what will happen when we lose that MetroE link if it's a static route.

Ahh, apologies, my mistake.

Well there are a few things to cover

1) you are receiving the route via BGP on your edge router. Are you redistributing that into EIGRP ?

2) the edge router will always think the best path is the MPLS network because EBGP has an AD of 20 whereas EIGRP has AD 90 and 170. Is this is a problem though because does any traffic from your internal LAN go to that router first ?

3) If you do 1) and redistribute into EIGRP and you also redistribute into EIGRP the static route on your L3 switch then you will have 2 routes for the same subnet and the route used will be the one with the lowest metric. From the perspective of the other L3 switch ie. the one not connected to the Metro-E link you need to make sure the preferred route is via the other L3 switch and not the edge router.

4) Because the link from the L3 switch is ethernet you need to check the availability of the remote end of the link because if that fails your L3 switch at this end might still think the link is up.

So i would do this -

1) You need to setup IP SLA on the 4500 L3 switch connected to the Metro ethernet switch

2) If the remote end is responding then you should install a route for 10.10.0.0/16 pointing to the remote end of the Metro Ethernet link.

3) On the same L3 switch you should redistribute the static route for 10.10.0.0/16 into EIGRP so your other L3 switch knows about it

4) Don't redistribute the BGP learned route into EIGRP on the edge router.

5) If the IP SLA fails ie. the next-hop is not available on the Metro-E link then install a static route pointing to the edge router on the L3 switch which again will get redistributed into EIGRP.

The above will ensure all traffic from the remote site uses the Metro-E connection except traffic from the edge router. If that is a problem ie. the edge router then let me know because we can modify the AD of the 10.10.0.0/16 route on the edge router so it prefers the Metro-E connection as well.

Jon

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Apologies if this gets formatted strange, I'm trying to reply via email.

I see now, that makes sense. I'm assuming I could do the same on the other end of the metroE if the topologies are the same or close to it? That should give me true WAN redundancy then for this site.

Are there any other options that still give us redundancy? I'm just asking because my team is starting to get nervous the more complex our setup gets, and I need to learn to put them at ease.

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Robert

Understood about the complexity but the key issue is the IP SLA and the nature of ethernet. Because the link could go down at the far end but your end doesn't realise it any solution not using IP SLA could lead to blackholing traffic. And if you have to use IP SLA then the rest of it is quite simple actually.

You could remove the IP SLA, redistribute the same route ie. 10.10.0.0/16 from the edge router and the L3 switch and use offset-lists in EIGRP to make sure the Metro-E is used but you don't protect against a far end failure.

If you don't have the spare equipment to set this up you could look at dynamips on a PC with a lot of memory and CPU horsepower and configure IP SLA for your team to get familiar with. IP SLA is one of those things that looks quite complex from the docs but makes a whole lot more sense when you see it in action.

Jon

I'll do some research on the IP SLA.

If we were running a dynamic routing protocol on both ends we could use that to monitor far end reachability and wouldn't need to rely on IP SLA.

Robert

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Robert

If we were running a dynamic routing protocol on both ends we could use that to monitor far end reachability and wouldn't need to rely on IP SLA.

Correct.

Jon